It is common practice in the medical field to use a medicinal container holding plural ingredients separately which are to be mixed immediately before administration. For example, a transfusion solution for IVH (intravenous hyperalimentation), which is composed of carbohydrate, amino acid, and electrolyte as a nutrient source, is stored in a compartmented container holding individual ingredients in separate compartments, thereby protecting glucose and amino acid from deterioration by Maillard reaction, and these ingredients are mixed together immediately before administration.
There are many granted or pending patents (as follows) for the compartmented container with two or more compartments separated from each other which is designed for internal mixing (for example, Patent Document 1: Japanese Patent No. 2675075, Patent Document 2: Japanese Patent No. 2675049, Patent Document 3: Japanese Utility Model Laid-open No. Hei 5-5138, Patent Document 4: Japanese Patent Laid-open No. Hei 8-299099, Patent Document 5: Japanese Patent Laid-open No. Hei 8-229100.) According to these patents, the compartmented container has two or more compartments separated by a weakly sealed part formed therein, so that it permits two or more contents to be mixed in the container without opening the container by rupturing the weakly sealed part by hand or jig (to make compartments join together) at the time of use.
Patent Documents 1 and 2 listed above disclose a compartmented container which is characterized in that the weakly sealed part has a seal layer formed from a mixture of a linear low-density polyethylene resin and a polypropylene resin. Therefore, this seal layer is likely to soften during sterilization at 121° C., resulting in breakage or deformation of the container.
Patent Document 3 listed above discloses a method for producing a compartmented container by inserting in a container a tape (or sheet) capable of weak sealing. This tape is formed from a mixture of polyethylene and polypropylene, and hence it is unsuitable for sterilization at 121° C. as in the case of Patent Documents 1 and 2.
Patent Documents 4 and 5 listed above disclose a compartmented container having a heat-sealable layer formed from a composition of polyethylene and olefin block copolymer or from a composition of polypropylene-based polymer and styrene-based elastomer. These polymer compositions are poor in heat resistance because of a high content of α-olefin and elastomer and hence are unsuitable for sterilization at 121° C.
On the other hand, it is also an important factor for containers to perfectly withstand an impact at the time of dropping, for example, to pass the drop test specified in the Food Sanitation Law. The standard of seal strength required for the drop test varies depending on the weight of the content. A container holding 500 mL of liquid, for example, differs from a container holding 1 liter of liquid in heat seal strength required to prevent breakage at the time of dropping. This applies also to the weakly sealed part of a compartmented container.
Therefore, thinking of the weakly sealed part (separator) of a compartmented container, it follows that its seal strength should be comparatively low if the content is less than 500 mL. The weakly sealed part does not need a high seal strength to prevent breakage because the container itself is small. An excessively high seal strength rather makes the weakly sealed part take a long time to break. On the other hand, its seal strength should be comparatively high if the content is 500 mL or more. The weakly sealed part needs a high seal strength because the container is large and the weakly sealed part is subject to a large load at the time of dropping. The weakly sealed part with an excessively low seal strength is likely to break due to the heavy load.
One conventional way to adjust the seal strength of the weakly sealed part of a compartmented container was to change the heat sealing temperature. Unfortunately, the range of change that can be achieved is limited to only about 20° C. (See Patent Document 6: Japanese Patent Laid-open No. 2003-52791.) Thus the conventional technology needs improvement to be able to control the heat seal strength of the weakly sealed part easily and freely in response to the weight of the content in a compartmented container.
There has been a demand for a compartmented container which permits the weakly sealed part to be formed at widely ranged temperatures.
The present invention was completed in view of the foregoing. It is an object of the present invention to provide a compartmented container which withstands sterilization at 121° C. or above without deformation, permits the weakly sealed part to keep its weak seal strength stable even after sterilization, and has good transparency, and which also permits the weakly sealed part to have a seal strength that can be controlled easily and freely.